To determine the efficacy of Mycobacterium bovis purified protein derivative (PPD) tuberculin as compared to that of the standard veterinary mammalian tuberculin in the early detection of naturally acquired tuberculosis in rhesus monkeys. Approximately 50 tuberculous monkeys will be isolated and their comparative skin reactivity to veterinary tuberculin and PPD will be determined. Twelve to 20 tuberculosis-free monkeys will then be paired with tuberculous monkeys. Weekly skin reactions will be measured and photographed and lymphocyte transformation studies performed. On diagnosis of tuberculosis in the conditioned monkey, the pair will be killed and necropsied. Tissue samples will be collected for histopathologic evaluation and Mycobacterium isolation and identification.